> I would like to see Proto4 include an option for compression
> (zlib,bz2) or somesuch and become self-decompressing upon unpickling.

I don't see what this would bring over explicit compression:
- depending on the use case, you may want to use different compression algorithms, e.g. for disk you may want higher compression ratio like bzip2/lzma, but for wire you'd prefer something fast like snappy
- supporting multiple compression algorithms and levels would complicate the API
- this would probably complicate the code, since you'd have to support optional compression, and have a way to indicate which format is used
- that's really mixing two entirely different concepts (serialization vs compression)